1. Field of the Invention
The present invention relates to a position estimation system which estimates a position of a mobile communication terminal such as a cellular phone based on information received from a wireless base station in an environment where the mobile communication terminal cannot communicate with a GPS (Global Positioning System).
2. Description of the Related Art
Conventionally, there is a technology for a mobile communication terminal whose transmission method is W-CDMA (Wideband-Code Division Multiple Access) to estimate its own position through communication with a wireless base station in an environment where the terminal cannot communicate with a GPS.
For example, as described in JP 2006-33207A, the wireless base station stores a transmission time, calculates an RTT (Round Trip Time) using a received signal from the mobile station, and calculates a distance from a calculated time stamp. Then, after completing demodulation of DPCCH (Dedicated Physical Control Channel), the wireless base station calculates a fading correlation value using a channel estimation value, performs rate calculation processing, and performs processing of estimating a moving direction from the ration between “0” and “1” in a bit sequence. Further, after the wireless base station estimates a distance, a speed, and the moving direction, the station determines an optimal position information that is to be sent to the mobile station using a table for determining transmission position information. Thus, as a technology in a broader concept, a wireless base station is allowed to estimate position information to be provided to a mobile communication terminal in the range of area in a sector.
JP 2006-33207A also describes that a wireless base station estimates to determine which sector a mobile communication terminal exists, in a radio area of a wireless base station. However, since position estimation can be performed just in units of sector areas and thus is fairly rough, there is a problem that more accurate position estimation such as positioning in latitude and longitude cannot be performed.